Thanks for stopping by and commenting. It appears that some of the studies surveyed in the CRS report do deal with petroleum coke in various ways, but many do so inconsistently, and to your point, they may not fully account for emissions associated with any coke exported outside of the refinery for use in power plants or steel production. Here is what CRS says about the studies they survey:
Treatment of Petroleum Coke. Petroleum coke (a source of excess carbon) is a co-product of bitumen production at both the upgrader and the refinery. Roughly 5%-10% of a barrel of crude ends up as coke; and the heavier the crude, the greater the percentage of coke. Bitumen refining can produce about 50% more coke than the average conventional crude. The treatment of coke is a primary driver behind the results of any WTW GHG oil sands crudes assessment. If coke is combusted (i.e., for process heat, electricity, or hydrogen production at the upgrader in lieu of natural gas combustion), WTW GHG emissions may increase anywhere from 14% (TIAX 2009) to 50% (McCulloch 2006) over lighter crudes. If it is stored, sold, and/or combusted elsewhere, its potential emissions may not be factored into the LCA. The main concern for modeling is ensuring that coke produced at the upgrader (for SCO) is treated consistently with coke produced at the refinery (for dilbit or other imported crudes). Based on the studies analyzed in this report, petroleum coke at the upgrader is either (1) consumed (for process heat, electricity, or hydrogen production); (2) stored; or (3) sold as a fuel for combustion. In contrast, the studies assume that petroleum coke produced at the refinery that is not consumed by the refinery itself is either (1) used to back out coal combustion for electricity generation; or (2) allocated outside of the LCA. These inconsistent methodologies make comparisons problematic. Coke produced at U.S. refineries has a low domestic demand, and is therefore often shipped to overseas markets for use as a replacement fuel for coal combustion or steel production (most studies include neither the overseas transportation nor the combustion emissions of coke in WTW GHG emissions assessments).
As I understand it, your study assumes that all petcoke produced as a byproduct of upgrading bitumen is exported from the refinery and used to fuel coal-fired power plants. Additionally, you assume that all petcoke consumed in this manner is in addition to any coal normally consumed in power plants, that is, you do not assume that the petcoke displaces any existing coal use but rather increases combustion at coal-fired power plants ton-for-ton.
That scenario depends on an assumption that there is no supply/demand rebalancing as a result of additional supplies of petcoke. That is consistent as well with your methods for treating tar sands bitumen as well -- e.g. you assume 100% of the carbon content in the bitumen is additional, that is, it does not displace any other crude oils and increases global oil consumption barrel for barrel.
Those are consistent assumptions, but as I indicated in my column, there are a range of alternative assumptions that are also plausible. Indeed, the whole debate hinges on what assumptions you make.
In effect, your report appears to offer a useful estimate of the extreme high-end of the possible range of emissions impacts of the Keystone XL pipeline: if 100% of the capacity of the pipeline carries new tar sands production that would not have been produced absent the construction of the pipeline, if that new tar sands crude increases global oil consumption barrel for barrel (e.g. it is 100% incremental to global consumption) and doesnt displace any other crude oil consumption, and if all petcoke produced as a byproduct is similarly 100% incremental to global coal combustion, then you arrive at the emissions estimate in your report (or somewhere close).
As you admit though, "we did not attempt to calculate incremental emissions, as calculating those depends on multiple assumptions regarding oil supply and demand." Indeed, that was the whole point of this column, to make those assumptions transparent and allow readers to decide which they think are most plausible. I have a hard time however seeing how you can then arrive at the conclusion that "what we have is an estimation of the actual emissions associated with the project."
In fact, the "actual emissions" associated with the project depend on which of the range of assumptions above (or another alternative scenario) prove to be the real-world outcome of building the project. Your report provides just one plausible outcome, at the highest end of emissions scenarios. Unfortunately, your report doesn't really acknowledge that, nor did the subsequent communications by anti-Keystone campaigners (including 350.org) who used your study to communicate the alleged climate impacts of the Keystone pipeline. In fact, it was one such communication that prompted me to dig into this question and write this column.
Anyway, thanks for commenting.